Typically, the natural gas burners that provide energy for a glass melting furnace, are located in the walls of the furnace. The flames from the burners extend across the width or the length of the furnace, slightly above and approximately parallel to the top surface of the glass melt within the furnace. Heat energy is transferred from the burner flames to the top surface of the glass melt primarily by conduction and radiation. In a typical furnace, raw batch materials are added to the furnace by distributing the raw materials on top of the existing glass melt, creating a batch ‘blanket’ of raw materials on the top surface of the glass melt. The raw batch materials consist of dry particles, ranging in grain size from approximately 0.02 to 1.0 mm.
Adding the raw batch materials into a glass furnace in this manner presents several operational difficulties. First, the dry batch materials are poor conductors of heat due to their low heat transfer coefficients and radiation emissive factors. As a result, the blanket of raw batch materials on the surface of the melt functions as an insulating layer that decreases the amount of heat energy that is transferred from the burners to the glass melt.
Another issue is the disturbance of the dry materials by the glass burner flames. The flow of air from the flames causes turbulence that disturbs and picks up the dry materials. The dry materials become entrained in the exhaust gases that exit the furnace flue or stack, a situation referred to as ‘batch carryover’, resulting in environmental air emissions such as opacity and particulate matter emissions. A third issue caused by the blanket of dry batch materials is the loss of light chemical elements such as sodium from the glass melt due to volatilization of these light elements. The loss of batch materials due to carryover or volatilization alters the chemistry of the glass melt, resulting in a final glass chemistry that is outside of the desired chemical specification, which alters the properties of the final glass product. To avoid these problems with dry batches, glass melting furnace feedstock is typically wetted with water (0-5% by weight). Although batch wetting mitigates many of the problems discussed herein, it can cause others such as poor batch transport conditions, segregation, and additional energy consumption in the glass melting furnace to drive off the added water.
The present disclosure embodies a number of aspects that can be implemented separately from, or in combination with, each other.
A glass furnace in accordance with one aspect of the disclosure includes a melt chamber configured to contain a glass melt, a conveyor configured to receive glass batch material and feed such material to the melt chamber, and a dam wall disposed upstream with respect to the melt chamber and downstream with respect to the conveyor, wherein a top of the dam wall is below a melt level in the melt chamber, and wherein the dam wall forms a well upstream of the melt chamber. The glass furnace also includes a heater positioned in the well and configured to heat glass batch material prior to flow over the dam wall, wherein the conveyor is disposed at a position below a top surface of the glass melt within the melt chamber. The conveyor is configured to drive the raw batch materials into a lower portion of the well for partial melting by the heater prior to entering the melt chamber, wherein the conveyor and the dam wall are configured to flow the batch materials upward over the dam wall before the batch materials enter the melt chamber.
In accordance with another aspect of the disclosure, a glass furnace includes a melt chamber configured to contain a pool of glass melt having a melt level, a feed chamber proximate a bottom portion of the melt chamber, the feed chamber having an outlet below the melt level, and a conveyor configured to receive batch material and to convey the batch material through the feed chamber toward the outlet of the feed chamber, the conveyor being disposed at least partially within the feed chamber. The glass furnace also includes a dam wall disposed upstream with respect to the melt chamber and downstream of the conveyor, wherein a top of the dam wall is below a melt level in the melt chamber, and wherein the dam wall forms a well upstream of the melt chamber. The glass furnace further includes a heater positioned in the well proximate the outlet of the feed chamber and configured to heat glass batch material prior to flow over the dam wall and that at least partially melts the batch material. The conveyor is disposed at a position below a top surface of the glass melt within the melt chamber, wherein the conveyor is configured to the raw batch materials into a lower portion of the well for partial melting by the heater prior to entering the melt chamber, and wherein the conveyor and the dam wall are configured to flow the batch materials upward over the dam wall before the batch materials enter the melt chamber.